Jason,
all that is true; but given the number of "boosted or improved or outright fake" lugers and the $$ value of certain varieties- logic does not always apply.
I said "at least not definitively", so until that serial number shows up in period documentation it is suspect to me, and its provenance is unknown. The fact that the upper is over 100 numbers before the first documented Test Eagle does not help.
I agree it could have been done with knowledge and intent; but intent to what ?
Perhaps as you speculate: repaired in service; or maybe just a luger lower restored for shooting, at some time in the past with a close numbered upper?
The person who "repaired or restored" that lower - may or may not have known it had any desirability other than being a "luger". JMHO
All that said, even a well worn old model with a TE lower is very nice to have !
